Fermentation (Catabolic Pathways & Production of ATP)
(compounds that can participate in exergonic reactions can act as fuel. Enzymes help break down complex molecules, rich in potential energy, to simpler waste products and converted to energy, while rest is lost in heat.)
Partial Degradation of sugars that occur without oxygen.
Cellular Respiration (Catabolic Pathways & Production of ATP)
Aerobic Respiration - (most prevalent and efficient) an oxygen, used as a reactant, and organic fuels are consumed. Most eukaryotic and prokaryotic cells carry out A.R.
Anaerobic Respiration - Harvest chemical energy without oxygen. Some prokaryotic cells use other reactants, other than oxygen, in a similar process as aerobic respiration.
- Includes both Aerobic and Anaerobic Respiration.
- However, Synonymous with Aerobic Respiration, because of the relationship with organismal respiration, in which animals breathes in oxygen.
Cellular Respiration (similar to a car burning fuel and reacting with oxygen)
- Food provides fuel and the exhaust is carbon dioxide and water.
- Organic Compounds + Oxygen --> Carbon Dioxide + Water + Energy.
Steps of cellular respiration by tracking the degradation of the sugar glucose (C6H12O6)
(Carbohydrates, fats, and proteins also can be processed and consumed as fuel)
- C6H12O6 + 6 O2 ---> 6 CO2 + 6 H2O + Energy (ATP+ Heat)
- (glucose is the fuel cells most often use)
- (breakdown of glucose is exergonic = having free energy, - change of G, occur spontaneously, i.e. without input of energy)
(In many chemical reactions there is a transfer of 1 or more electrons from 1 reactant to another.)
These electron transfers are called redox reactions.
Oxidation (in redox reactions)
the loss of electrons from one substance
Reduction (redox reactions)
- the addition of electrons to another substance
- (Note: adding electrons is called reduction; - charged electrons added to an atom reduces the positive charge of an atom.)
Ex. Generalized Redox Reduction:
Xe- + Y ---> X + Ye-
Reducing Agent is the donor, substance Xe-; it reduces Y, Y accepts the donated electron.
Ex. Generalized Redox Reaction:
Xe- + Y ---> X + Ye-
Oxidizing Agent = the electron acceptor, substance Y; it oxidizes Xe- by removing its electrons.
NAD+ (nicotinamide adenine dinucleotide)
- an electron carrier/coenzyme.
- Each electron travels with a proton, in the case of glucose- thus a hydrogen atom. Hydrogen atoms are not directly transferred to Oxygen, instead they are passed first to an electron carrier, NAD+.
(Dehydrogenases transfer electrons from substrates to NAD+, forming NADH. Electrons go down electron transport chain to Oxygen, forming water. Then Energy is released).
The energy that is released at each step of the chain is stored in a form of the mitochondrion can use for ATP. ATP synthesis powered by redox reactions of the electron transport chain is called Oxidative Phosphorylation.
Glycolysis - occurs in cytosol and begins degradation of glucose into two pyruvate molecules.
Citric Acid Cycle - (occurs in mitochondrial matrix of eukaryotes and cytosol of prokaryotes) completes breakdown of glucose by oxidizing a derivative of pyruvate into carbon dioxide.
10% of ATP formed by glycolysis and citric acid cycle by a mechanism called Substrate-level Phosphorylation.
Acetyl CoA (in mitochondrion)
(After molecular oxygen is present, pyruvate enters a mitochondrion in eukaryotic cells.)
(Sulfur containing compound derived from a B vitamin)
Pyruvate enters mitochondrion via active transport, and is first converted to a compound called Acetyl CoA (Acetyl Coenzyme A)
a.k.a. citric acid cycle is also called the tricarboxylic acid cycle
The cycle functions as a metabolic furnace that oxidizes organic fuel derived from pyruvate.